MRI scans found to improve prostate cancer diagnosis

Using MRI as a screening test alongside prostate specific antigen (PSA) density allows detection of cancers that would have been missed by the blood test alone, according to research conducted by University College London (UCL), University College London Hospitals NHS Foundation Trust (UCLH) and King’s College London, and published in BMJ Oncology.

Currently, men over 50 in the UK can ask for a PSA test if they are experiencing symptoms or are concerned about prostate cancer. Previous screening studies have used a PSA level of 3 ng/mL or above as the benchmark for performing additional tests to look for prostate cancer, such as a biopsy.

Though previous research found that the combination of a PSA test and/or digital rectal examination, followed by a biopsy if disease is suspected, helped to reduce prostate cancer mortality by 20% after 16 years, this approach has also been linked to overdiagnosis and overtreatment of lower-risk cancers. In recent years, the introduction of MRI as a first step in investigating men at higher risk of prostate cancer has spared one in four men from an unnecessary biopsy.

For the REIMAGINE study, researchers invited men aged 50 to 75 to have a screening MRI and PSA test. Of the 303 men who completed both tests, 48 (16%) had a positive screening MRI that indicated there might be cancer, despite only having a median PSA density result of 1.2 ng/mL. 32 of these men had lower PSA levels than the current screening benchmark of 3 ng/mL, meaning they would not have been referred for further investigation by the PSA test currently in use.

After NHS assessment, 29 men (9.6%) were diagnosed with cancer that required treatment, 15 of whom had serious cancer and a PSA of less than 3 ng/mL. Three men (1%) were diagnosed with low-risk cancer that did not require treatment.

“The thought that over half the men with clinically significant cancer had a PSA less than 3 ng/mL and would have been reassured that they didn’t have cancer by a PSA test alone is a sobering one and reiterates the need to consider a new approach to prostate cancer screening,” said chief investigator Professor Caroline Moore, from UCL’s Division of Surgical & Interventional Science.

“Our results give an early indication that MRI could offer a more reliable method of detecting potentially serious cancers early, with the added benefit that less than 1% of participants were ‘overdiagnosed’ with low-risk disease. More studies in larger groups are needed to assess this further.”

The next step towards a national prostate cancer screening program is already underway, with the LIMIT trial being conducted with a much larger number of participants. If LIMIT is successful, a national-level trial would be required before prostate cancer screening becomes standard clinical practice.

“The UK prostate cancer mortality rate is twice as high as in countries like the US or Spain because our levels of testing are much lower than other countries,” said senior author Professor Mark Emberton, also from the Division of Surgical & Interventional Science. “Given how treatable prostate cancer is when caught early, I’m confident that a national screening program will reduce the UK’s prostate cancer mortality rate significantly.”

Image credit: UCLH.